This invention relates to a polyetheramide-imide polymer composition, more particularly to a polyetheramide-imide polymer composition excellent in film-forming properties at low temperatures.
In the fields of electrical insulating materials, coating compositions usable at high temperatures, films, etc., wherein heat resistance and solvent resistance are required, thermosetting resin compositions such as epoxy resin compositions, polyimide resin composition, etc. have only been used. But film-forming of these thermosetting resin compositions disadvantageously requires a curing reaction at high temperatures with heating or a curing reaction for a long period of time.
On the other hand, when a substrate cannot be heated at high temperatures while solvent resistance and heat resistance are required, it is almost impossible to use thermosetting resin compositions heretofore being known and almost no compositions can be used for such a purpose. Examples of such substrates are insulating substrates for circuits mounting various kinds of electronic parts, coatings of plastic vessels portions of which contact with an organic solvent, orientation controlling films used in liquid crystal display devices using plastic films as substrates and such substrates, and the like.
In order to solve such a problem, polyamide-imide polymers belonging to thermoplastic resins are expected to be a preferable material. But the polyamide-imide polymers dissolve in a high boiling-point nitrogen-containing polar solvent such as N,N-dimethylacetamide, N-methylpyrrolidone, or the like, but hardly dissolve in a usual low boiling-point organic solvent such as tetrahydrofuran, dioxane, cyclohexanone, or the like. Therefore, there is a limit in film-forming properties at low temperatures.
On the other hand, polyetheramide-imide polymers improved slightly in solubility in a usual low boiling-point organic solvent maintaining high heat resistance of aromatic polyimides and polymeric polyamides are disclosed in Japanese Patent Unexamined Publication No. 59-202259. But since these polymers contain a large amount of amide bonding units derived from aromatic dicarboxylic acids, it is necessary to co-use the above-mentioned high boiling-point nitrogen-containing polar solvent and it is difficult to make a solution by using only a usual low boiling-point organic solvent.